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Storms Storms • A storm is a violent disturbance in the atmosphere • 4 major types of storms: – Thunderstorms – Tornadoes – Hurricanes – Winter Storms • A meteorologist is a scientist who studies weather and tries to predict it Thunderstorms • A thunderstorm is a small storm often accompanied by heavy precipitation and frequent thunder and lightning. • Form in large cumulonimbus clouds (also called thunderheads) on hot, humid afternoons Thunderstorms • Warm, humid air rises rapidly and the air cools, forming dense thunderhead clouds • Heavy rain falls, sometimes along with hail • Within the thunderhead cloud there are strong updrafts and downdrafts Lightning • Lightning is a sudden spark, or electrical discharge • Positive and negative charges jump between parts of a cloud, or between nearby clouds, or between a cloud and the ground Thunderstorms • Lightning heats the air to 30,000oC • Thunder is the sound of the rapidly heated air expanding suddenly and explosively • Light travels faster than sound so you see lightning before you hear thunder Calculating Lightning Distances • Watch the sky for a flash of lightning. • Count the number of seconds until you hear thunder. • Divide the number of seconds by 5 to calculate the distance the storm is away from your location in miles (or divide by 3 for kilometers). • Ex: If you counted 18 seconds from when you saw the lightning, the strike was 3.6 miles (6 kilometers) from your location. Divide Number of Seconds by 3 for Distance in Km or 5 for Distance in Miles. Examples of types of Lightning • • • • • • • • • Spider-Flashes of spider lightning crawl across the sky for up to 90 miles. Sheet lightning - Normal lightning that is reflected in the clouds Heat lightning - Normal lightning near the horizon that is reflected by high clouds Ball lightning - A phenomenon where lightning forms a slow, moving ball that can burn objects in its path before exploding or burning out Red sprite - A red burst reported to occur above storm clouds and reaching a few miles in length (toward the stratosphere) Blue jet - A blue, cone-shaped burst that occurs above the center of a storm cloud and moves upward (toward the stratosphere) at a high rate of speed Ribbon lightning-Ribbon lightning occurs in thunderstorms with high cross winds and multiple return strokes. The wind will blow each successive return stroke slightly to one side of the previous return stroke, causing a ribbon effect. Bead lightning- Bead lightning is a type of cloud-to-ground lightning which appears to break up into a string of short, bright sections, which last longer than the usual discharge channel. It is fairly rare. Forked lightning-Forked lightning occurs when a second lightning stroke doesn't follow the same path as the first lightning stroke. Thus, it appears forked. Lightning Strikes in the U.S. • This map shows how often lightning strikes different parts of the lower 48 states. Central Florida has the most intense concentration of cloud-to-ground lightning because it has a lot of warm, humid air. The Pacific Northwest has almost no lightning. Thunderstorm Safety • Go INSIDE! • Do NOT touch anything that can conduct electricityespecially metal objects and bodies of water • Crouch down in a low area-avoid trees Tornadoes • A tornado is a rapidly whirling, funnelshaped cloud that reaches down from a storm cloud to touch Earth’s surface Tornado Formation • Warm, moist air flows in at the bottom of a cumulonimbus cloud and moves upward • A low pressure area forms inside the cloud • Warm air rotates as it meets winds blowing in different directions at different altitudes • Tornado Alley is an area of the United States that has a high frequency of tornadoes because cold, dry air moves south from Canada to meet warm, humid air from the Gulf of Mexico • 5 states that cross Tornado Alley are: – – – – – Texas Oklahoma Kansas Nebraska Iowa The Fujita Tornado Damage Scale • Tornadoes are ranked on the Fujita scale by the amount of damage they cause Tornado Safety • A tornado watch is an announcement that tornadoes are possible in your area. Stay tuned to the radio or television news. • A tornado warning is an announcement that a tornado has been sighted. Take shelter immediately! • The safest place to be during a tornado is in a storm shelter or the basement of a well-built building Hurricanes • A hurricane is a tropical cyclone that has winds of 119 km/h or higher • Hurricanes form in the Atlantic, Pacific, and Indian Oceans • In the western Pacific Ocean, hurricanes are called typhoons • A hurricane begins over warm ocean water as a low-pressure area, or tropical disturbance. • A hurricane draws its energy from the warm, humid air at the ocean’s surface • As the air rises and forms clouds, more air is drawn into the system • Inside the storm are bands of very high winds and heavy rains • Winds spiral inward toward the area of lowest pressure at the center Hurricane Names • Hurricanes are given names to help us identify them and track them as they move across the ocean • Men and women's names are used • One name for each letter of the alphabet except Q, U, and Z • World Meteorological Organization uses six lists in rotation • The only time a new name is added is if a hurricane is very deadly or costly • If that happens then the name is retired and a new name is chosen. 2008 2009 2010 2011 2012 2013 Arthur Bertha Cristobal Dolly Edouard Fay Gustav Hanna Ike Josephine Kyle Laura Marco Nana Omar Paloma Rene Sally Teddy Vicky Wilfred Ana Bill Claudette Danny Erika Fred Grace Henri Ida Joaquin Kate Larry Mindy Nicholas Odette Peter Rose Sam Teresa Victor Wanda Alex Bonnie Colin Danielle Earl Fiona Gaston Hermine Igor Julia Karl Lisa Matthew Nicole Otto Paula Richard Shary Tomas Virginie Walter Arlene Bret Cindy Don Emily Franklin Gert Harvey Irene Jose Katia Lee Maria Nate Ophelia Philippe Rina Sean Tammy Vince Whitney Alberto Beryl Chris Debby Ernesto Florence Gordon Helene Isaac Joyce Kirk Leslie Michael Nadine Oscar Patty Rafael Sandy Tony Valerie William Andrea Barry Chantal Dorian Erin Fernand Gabrielle Humberto Ingrid Jerry Karen Lorenzo Melissa Nestor Olga Pablo Rebekah Sebastien Tanya Van Wendy Hurricane Formation Hurricanes • Hurricanes last longer than other storms, usually a week or more • After a hurricane passes over land, it no longer has warm, moist air to draw energy from so it loses strength • A storm surge is a “dome” of water that sweeps across the coast where a hurricane lands • For safety during a hurricane, people are told to evacuate • Evacuate means to leave the area immediately Winter Storms • All year round, most precipitation begins in clouds as snow • A large amount of humid air that cools below 0oC can produce a winter storm • Lake Effect Snow-areas east of the Great Lakes get a LOT of snow WHY? Lake-Effect Snow • The land cools much more rapidly than the water in the Great Lakes (or any lake) • When a cold, dry air mass from central Canada moves southeast across one of the Great Lakes, it picks up water vapor and heat from the lake • As soon as the air mass reaches the other side of the lake, the air rises and cools again • The water vapor condenses and falls as snow • Cities such as Buffalo and Rochester, New York are two of the snowiest cities in the U.S. because they are located east of the Great Lakes Lake Effect Snow
